A photodetector array comprises a plurality of spaced-apart elements, such as P-I-N or avalance detectors, in a quadrant, linear, or rectangular arrangement. The spacing between the elements of the array is kept as small as possible, consistent with electrical isolation of the elements, in order to increase the position-sensing capability of the array and to decrease the loss of carriers generated by light incident on the array between the elements. For an avalanche photodiode array the avalanche gain is also reduced because the electric field in the region between the elements is greatly reduced. Thus such arrays have high response regions about the P-N junctions of the elements in which photogenerated charge undergoes high avalanche gain. Between these high response regions are low response regions in which the gain is reduced to about unity corresponding to, but wider than, the regions between the elements.
McIntyre et al. in U.S. Pat. No. 4,458,260, filed Nov. 20, 1981 and incorporated herein by reference, have disclosed an avalanche photodiode array wherein the spacing between the elements has been reduced to a width of approximately 75 micrometers (.mu.m). While alternative fabrication procedures may be possible to reduce the width of this region, it is unlikely that it can ever be eliminated. Such wide low response regions, particularly for an avalanche photodiode array, are unacceptable in many applications.